July in the hills with Chris Horne and Barbara Mitcalfe

Prumnopitys ferruginea, miro, brown pine

Miro is an endemic member of the Prumnopitys genus. Its ancestors began to appear in the Lower Cretaceous era, over 100 million years ago. It grows in lowland forests in the North, South and Rakiura/Stewart islands, up to 1,000 m elevation, often in the same ecosystems as rimu, and on similar soils.

Its botanical name is derived from Prumno = plum; pitys = coniferous tree; ferruginea = rust-coloured. Both miro and mataī used to be in the Podocarpus genus, but taxonomic research showed that miro and mataī differ significantly from the other podocarps. As a result, the Prumnopitys genus was set up to accommodate these two species. However, recent DNA analysis indicates that miro is not so closely related to mataī after all. Eventually it will be moved into a new genus, yet to be set up and named.

Miro trees can grow for up to 800 years, with trunks up to 25 m tall and 1.25 m in diameter. The dark grey bark falls off in rounded flakes, making the trunk look hammer-marked, but less obviously so than in mataī. Good places to see fine miro are Upper Hutt's Harcourt Park, Waiorongomai and Mt Ruapehu. On your tramps you may have noticed that young miro, up to 6-8 m high, have a graceful, weeping form.

Miro foliage and ripe ‘fruit’ Photo: JEREMY ROLFE

Miro’s bright, light-green juvenile leaves are up to 30 x 2-3 mm, curving, tapering and narrowly pointed. The adult leaves are 15 x 2-3 mm, dark green above, paler green below, and arranged in two opposite rows in one plane, more or less at right angles to the branchlets. They are distinctly shorter and less sharply pointed than the juvenile leaves, with a prominent mid-vein, and margins that curve downwards.

Reproduction

Miro are dioecious: female trees have female 'cones'; male trees have male 'cones'. The slim, upright, male 'cones', 12-15 x 3-4 mm, borne on specialised branchlets, turn yellow as their pollen ripens and is carried away by wind and/or bees. Unlike mataī, miro's male cones do not occur every year, and are not usually numerous.

The female cones are also borne on specialised branchlets and bear ovules containing the female sexcells which after fertilisation by pollen, develop into seeds. Each seed is enclosed within a fleshy 'fruit', up to 20 mm diameter, like a small, green, unripe plum. (See pages 96-98, NZ's Native Trees. Dawson and Lucas. 2011). They take about a year to mature, eventually turning bright red-purple.

Uses

Māori ate the fruit raw. It is rather sweet, but with a slight tang and smell, similar to turpentine. Māori squeezed an aromatic substance from the fruit to make a perfume, and an insecticide. They extracted gum from the bark to place on wounds to stop bleeding, and to heal ulcers. They also used the bark to make water containers. Bushmen made an antiseptic from an infusion of the bark.

Wool can be dyed maroon, mushroom or brown with an extract from the bark, depending on the mordant used. Miro timber, hard, durable and straight-grained, was popular for house frames, weather-boards and floors. It is now used to make furniture and for carving and wood-turning.

Kererū and tūī love the ripe fruit. They often fly long distances to gorge themselves on it, later depositing the seeds in ecosystems nearby or further afield. The role of kererū and tūī in indigenous ecosystem succession is extremely important.